Rain Water Is Excellent For Window Cleaning

You Shouldn’t Clean Windows In The Rain – Is That Really True?

Rain water is actually very good for window cleaning. Yes, all those people who say that you shouldn’t clean windows in the rain are actually wrong. OK, it used to be true, but that was back in the Industrial age, when the air was filled with industrial smog. The rain that came through that smog was contaminated with dirt, smoke, industrial pollution etc. In fact in the UK and Ireland, acid rain was much more common than it is today due to the pollutants that were picked up by the rain from industrial air pollution. And all that pollution only made the rain water dirty, so what was the difference between cleaning windows in the rain and cleaning them ‘before’ the rain? And if you live in the UK or Ireland, then for more than half the year, you are never far from a rain shower anyway. Well, err…

Rain Water Is Harvested By Window Cleaners

Nowadays, the story is different and rain water is actually harvested (collected) by many window cleaners, and used to clean customers windows. Yes, instead of avoiding rain water, professional window cleaners are actually using it to clean windows in preference to tap water. Don’t believe me? Do an online search for “rainwater harvesting window cleaning”.

Rain Water Has Fewer Contaminates Than Tap Water

Rain water normally contains far fewer contaminates in solution than tap water in many parts of the country, and it more suited to cleaning and removing dirt than ‘clean’ tap water. If you measure the number of contaminates in solution in rainwater using a TDS meter, the reading ranges from very low to zero in many parts of the country. Whereas, tap water normally has between 30 – 200 times more solids dissolved into it. These figures are important to window cleaners, and you can read some more on how we do it in this article – What Is TDS and Why Is It Important To Window Cleaners.

Wait! I have Seen Dirty Windows After The Rain

Yes, sometimes a window does look more dirty after the rain. This generally happens if the window hadn’t been clean in a while, and the rain shower was only light on the glass – not a wash out.

Sometimes after a light shower, you can see dirty streaks on your windows. Well, these aren’t actually from new dirt, but existing dirt on the window. A raindrop lands on the glass and starts to run down it. As it goes, it absorbs some of the dirt on the glass (remember the lack of dissolved solids we just discussed in rain water). We know that a drop of water tries to stay as a drop / a lump / a bump of water, this is because of the physics of surface tension, anyway… The drop creates a line. This line is outlined with both the dirt already on the glass at the edge of the clean streak, and some of the dirt which was absorbed by the drop and deposited to the outside of the drop – NOT new dirt. The dirt deposited to the outside of the drop is due to the science of surface tension and absorbency & saturation.

As well as this, if the rain stops and the rain drop evaporates, the absorbed dirt is then deposited on the glass in one point where the rain drop was. This creates a dense area of dirt – the dirt that was absorbed in the rain drop.

So, taking all of this into consideration, when you look at a window after the rain, you can see the outlined streak of the path of the raindrop. It makes the window look dirtier to you, when in actual fact, it isn’t. A line has been created in the glass, outlined with dirt already there and ending in a smear of dirt which is prominent to the eye. So, although all that has happened is that the dirt already on the glass has been repositioned by the clean rain water, it looks like the rain has made the window dirty!

Dirty Windows In The Autumn & Winter

You may have noticed that your windows actually get dirtier in the Autumn and Winter when there is more rain, so how come if the rain doesn’t make them dirty? Well, not only does it rain, but it is also more windy and that are more storms. Dirt is actually carried in the wind and storms, and that is what causes most problems. And for those of us close to the sea, you know that sea water can be carrier in the air too, and that makes creates a white haze over your windows with the sea salt. It’s not the rain that makes them dirty, it’s the dirt and salt etc. carried on the wind that causes most of the problems.

Can You Clean Windows In The Rain?

So, yes you can clean windows in the rain. The next time you see your window cleaner out in the rain, don’t think “he shouldn’t be cleaning windows in the rain”. Instead feel sorry for him, because frankly it’s miserable working outside in that weather. Cleaning windows in the rain is not a problem – rain water is normally clean – cleaner than tap water.

OK, there is one other thing that makes a difference when cleaning windows ‘in’ the rain. If you use the traditional style of window cleaning, it is more difficult to finish them when it is raining – not impossible, but it is more difficult. So, that is just a problem for the window cleaner, not the owner of the windows. Anyway, this doesn’t apply to me, as I generally do not use the traditional method, but a pure water cleaning technique. This technique is not affected by the rain, so anyone using this method can happily clean widows in the rain with no ill effects to the windows.

Do ‘I’ Clean Windows In The Rain?

Yes, I do. I offer a regular service to my customers, and if I am going to do that, then I need to be out working in the rainy days too. I offer a 100% satisfaction guarantee anyway, if I have cleaned your windows (raining or not) and they are not cleaned right, I will happily do them again for free. I would rather clean them again, and you be happy, rather than you be unhappy with my service. So, I ‘put my money where my mouth is’ regarding cleaning windows in the rain.

Some days it is raining too heavily for practical or sometime safe working conditions. Then, on those days I do not clean windows. Otherwise, yes you will see me out working in the rain, as my customers want a regular, reliable service, and it makes no difference at all to the finished cleanliness of your windows.

So, forget about the myth about not cleaning windows in the rain – it’s just an ‘old wives tale’ and doesn’t apply in today’s climate or my window cleaning method.

Hi Rich,
It’s doubtful that you can buy rainwater, but I do know a number of professional car detailing companies use de-ionised water. Not sure about the USA, but in the UK, there are a number of places that sell purified water to window cleaners and car detailing companies. Alternatively, you could purify your own water. If you don’t need much water and your TDS (total dissolved solids) aren’t too high, then you can get a de-ionisation vessel and resin, and purify your own water for your business.

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Snow Day today. Well, at least snow morning anyway. Did you know that you shouldn't wash windows in such low temperatures? It's because of 'thermal shock'. If there are any imperfections in the glass and you put hot water on freezing glass, it cracks. You don't see it as much now as we did with more single glazing. With single glazing the heat of the fire or radiator in the morning, could crack the single glazing window. Double glazing protects against that… unless hot water is put on the outside pane. Though it is all a bit more complex than that - like so much in life these days.